PTFs are available.
Interesting note about PAGEDEL and use of ESQA.
Best Regards,
Sam Knutson, GEICO
System z Performance and Availability Management
mailto:[EMAIL PROTECTED]
(office) 301.986.3574
"Think big, act bold, start simple, grow fast..."
APAR Identifier ...... OA20749 Last Changed ........ 08/05/02
PAGE DATASET SIZE LIMIT IS 16M SLOTS AT Z/OS R1.8
Symptom ...... IN INCORROUT Status ........... CLOSED PER
Severity ................... 3 Date Closed ......... 08/04/18
Component .......... 5752SC1CW Duplicate of ........
Reported Release ......... 730 Fixed Release ............ 999
Component Name 5752 AUX STOR M Special Notice ATTENTION
Current Target Date ..08/05/02 Flags
SCP ...................
Platform ............ PERVASIVE
Status Detail: SHIPMENT - Packaged solution is available for
shipment.
PE PTF List:
PTF List:
Release 730 : UA40555 available 08/04/30 (F804 )
Release 740 : UA40556 available 08/04/30 (F804 )
Parent APAR:
Child APAR list:
ERROR DESCRIPTION:
The MVS Initialization and Tuning Guide (SA22-71591-04) in
section 2.2 "Page Data Set Sizes" indicates page datasets can be
no more than 1M (1,048,576) slots (4GB) in size. As of z/OS
R1.8, this is no longer true, page datasets can now be allocated
as large as 16M (16,777,216) slots (64GB) in size.
HOWEVER, ASM still supports only up to 4G page datasets.
LOCAL FIX:
IDCAMS DEFINE PAGESPACE supports >4G page datasets at z/OS R1.8.
HOWEVER, ASM still only supports page datasets up to 4G in size.
PROBLEM SUMMARY:
****************************************************************
* USERS AFFECTED: Users of HBB7730 and HBB7740. The fix *
* is included in HBB7750. *
****************************************************************
* PROBLEM DESCRIPTION: ASM does not fully support page data *
* sets larger than 4GB. *
****************************************************************
* RECOMMENDATION: *
****************************************************************
Page data sets larger than 4GB can be defined as of z/OS1.8,
however various problems can occur when a page data set is
defined to be larger than 32,767 cylinders. Signed halfword
fields that represent the number of cylinders are treated
as negative values if the size of the data set exceeds 32,767
cylinders. This can result in incorrect comparisons or
operations on these fields.
Possible symptoms include:
- Increased aux slot usage due to slots not being freed
properly by module ILRFRSLT
- Incorrect page of data being paged-in from aux storage
PROBLEM CONCLUSION:
ASM is updated to support page data sets larger than 4GB.
PATCYLNO (ILRPAT) and other internal fields are redefined to
be unsigned in order to accommodate a maximum of 65,520
cylinders.
Documentation Updates
------------------------
Title - MVS Initialization and Tuning Guide
SRLs - SA22-7591-04 SA22-7591-06
|--- LOCATION IN PUBLICATION -----------------------------|
| |
| Chapter 2. Auxiliary Storage Management Initialization |
| Section: Page Data Set Sizes |
| |
|---------------------------------------------------------|
Current text:
Page data set sizes can affect system performance. The maximum
number of slots for a page data set is 1,048,576 slots
per data set. Note the following recommendations:
Updated text:
| Page data set sizes can affect system performance. The
| maximum number of slots for a page data set is 16,777,215.
| However, the size of a page data set will be limited
| by the amount of available space on the volume on which
| a data set is to be allocated. A 3390 device with 65,520
| cylinders contains 11,793,600 slots.
Note the following recommendations:
|--- LOCATION IN PUBLICATION -----------------------------|
| |
| Chapter 2. Auxiliary Storage Management Initialization |
| Section: Page Data Set Sizes |
| |
|---------------------------------------------------------|
Add a new section to describe the virtual storage usage
associated with each page data set.
| Storage Requirements for Page Data Sets
| ASM allocates storage in ESQA for every in-use page
| data set. This storage is obtained at IPL time for the
| data sets defined during IPL, and during processing of the
| PAGEADD command for data sets that are added dynamically
| after IPL.
| The amount of ESQA consists of a fixed amount (approximately
| 32,000 bytes) regardless of the page data set size, plus
| a variable amount that is determined by the size of the
| data set (24 bytes per cylinder).
|--- LOCATION IN PUBLICATION -----------------------------|
| |
| Chapter 2. Auxiliary Storage Management Initialization |
| Section: Performance Recommendations |
| |
|---------------------------------------------------------|
Current text:
1. Allocate only one paging data set per device. Doing this
reduces contention among more than one data set for use of
the device.
Updated text:
1. Allocate only one paging data set per device. Doing this
reduces contention among more than one data set for use of
| the device. If you do define more than one paging data set
| per device, use of Parallel Access Volume (PAV) devices
| can help to reduce contention for a device.
Title - z/OS MVS System Commands
SRLs - SA22-7627-15 SA22-7627-17
Documentation of the PAGEDEL command is updated to recommend use
of the REPLACE option as a way of avoiding the ESQA storage
usage associated with the DELETE option.
|--- LOCATION IN PUBLICATION -----------------------------|
| |
| Chapter 4, PAGEDEL Command |
| |
|---------------------------------------------------------|
Notes:
6. When issuing the PAGEDEL DELETE command, there is the
potential for significant storage usage. Several blocks of
storage in ESQA are obtained in order to process the
PAGEDEL command. This includes a x'500' byte block for
each cylinder on the deleted data set that contains
in-use slots. Some of this storage will remain in use
and not freed until all the in-use slots are freed, which
could be some time after the PAGEDEL has completed (as
indicated by message IEE205I).
| When possible, consider using the PAGEDEL REPLACE option
| instead of the DELETE option in order to avoid the ESQA
| storage usage associated with the DELETE option. With the
| REPLACE option, slots are migrated from the old data set
| directly to the new data set without the need to keep track
| of the location of the migrated slots (thus eliminating
| the need for extra ESQA storage).
Title - MVS Data Areas, Volume 3 (IVT - RCWK)
SRLs - GA22-7583-09 GA22-7583-10
Change PATCYLNO to unsigned.
|--- LOCATION IN PUBLICATION -----------------------------|
| |
| Chapter 2 Auxiliary Storage Management Initialization |
| Section: PAT Heading Information |
| |
|---------------------------------------------------------|
| 8 (8) UNSIGNED 2 PATCYLNO Number of cylinder maps
in this PAT
TEMPORARY FIX:
COMMENTS:
MODULES/MACROS: ILRFRSLT ILRFTPAG ILRIODRV ILROPS00 ILRPAT
ILRPDPAG ILRPGDEL ILRPGEXP ILRPREAD ILRTMI00
SRLS: SA22762717 SA22762715 SA22759104 SA22759106
GA22758309 GA22758310
RTN CODES:
CIRCUMVENTION:
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